[to #773] implement UpdateServiceGCSafePoint

[shiyuhang0]

What problem does this PR solve?

Issue Number: close #772

What is changed and how does it work?

Implement UpdateServiceGCSafePoint

Code changes

• Has exported function/method change
• Has exported variable/fields change
• Has methods of interface change
• Has persistent data change
• No code

Check List for Tests

This PR has been tested by at least one of the following methods:

• Unit test
• Integration test
• Manual test (add detailed scripts or steps below)
• No code

Side effects

• Possible performance regression, WHY: TBD
• Increased code complexity, WHY: TBD
• Breaking backward compatibility, WHY: TBD
• NO side effects

Related changes

• Need to cherry-pick to the release branch
• Need to update the documentation
• Need to be included in the release note
• NO related changes

[codecov]

Codecov Report

Patch coverage: 10.00% and project coverage change: +0.03 🎉

Comparison is base (dda1029) 38.09% compared to head (53f621d) 38.13%.

Additional details and impacted files

@@             Coverage Diff              @@
##             master     #723      +/-   ##
============================================
+ Coverage     38.09%   38.13%   +0.03%     
  Complexity     1613     1613              
============================================
  Files           278      278              
  Lines         17462    17482      +20     
  Branches       1984     1986       +2     
============================================
+ Hits           6653     6666      +13     
- Misses        10154    10155       +1     
- Partials        655      661       +6     

Impacted Files	Coverage Δ
src/main/java/org/tikv/common/PDClient.java	57.79% <0.00%> (-1.07%)	⬇️
src/main/java/org/tikv/common/util/Pair.java	53.84% <28.57%> (-29.49%)	⬇️
src/main/java/org/tikv/common/pd/PDError.java	0.00% <0.00%> (-30.31%)	⬇️
...java/org/tikv/common/operation/PDErrorHandler.java	40.00% <0.00%> (-20.00%)	⬇️
src/main/java/io/grpc/internal/ClientCallImpl.java	57.14% <0.00%> (-0.25%)	⬇️
...ty/handler/codec/http2/Http2ConnectionHandler.java	46.94% <0.00%> (ø)
...rc/main/java/io/grpc/netty/NettyClientHandler.java	56.03% <0.00%> (+1.93%)	⬆️
...y/handler/codec/http2/DefaultHttp2FrameWriter.java	40.92% <0.00%> (+1.98%)	⬆️
.../handler/codec/http2/Http2OutboundFrameLogger.java	85.71% <0.00%> (+4.76%)	⬆️
... and 2 more

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[ti-srebot]

@zhangyangyu, Thanks for your review. The bot only counts LGTMs from Reviewers and higher roles, but you're still welcome to leave your comments. get siglist: dial tcp 172.16.4.167:34000: connect: no route to host

[shiyuhang0]

/cherry-pick release-3.3

[ti-chi-bot]

@shiyuhang0: new pull request created to branch release-3.3: #732.

Details

In response to this:

/cherry-pick release-3.3

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